Facile construction of CoNi-MOF nanosheet arrays and exploration of the active sites for oxygen evolution reaction with ultralow overpotential

Developing efficient and inexpensive electrocatalysts for oxygen evolution reaction (OER) is currently a research hotspot in the field of water splitting for hydrogen production. In this work, a series of oriented CoNix-metal organic frameworks nanosheets (CoNix-MOFs, x = 0.23, 0.48, 0.96) were successfully prepared on carbon fiber paper (CFP) to form the CoNix-MOFs/CFP arrays by a facile construction. Electrochemical test results indicated that the optimized CoNi0.48-MOF/CFP exhibits the ultralow overpotential of 206 mV at a current density of 10 mA cm-2 and low Tafel slope of 37 mV dec-1. Moreover, an in-depth exploration of the active site shows that the actual active species is CoNi-MOF/CoNiOOH composite for OER. The excellent OER performance could be mainly attributed to the formation of low-crystalline CoNiOOH, electronic coupling between Ni and Co metals and the cross-linked nanostructure. This study will be helpful for expanding the sheet structural design of MOF catalysts and provide an example for the exploration of MOF active species.(c) 2023 Elsevier B.V. All rights reserved.